The disclosure of Japanese Patent Application No. 2000-380531 filed on Dec. 14, 2000, including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to a vehicle control apparatus and a vehicle control method capable of continuing an appropriate control operation even if a vehicle collides with another object.
2. Description of Related Art
Impact reducing apparatus for reducing the impact caused by a collision of a vehicle with an object have been proposed. For example, Japanese Patent Application Laid-Open No. 9-136659 discloses an apparatus that, if a yaw moment acts on the vehicle, reduces the impact on the vehicle by steering the vehicle""s rear wheels to such a direction as to promote a yaw motion of the vehicle. Also disclosed is a technology that reduces the impact while maintaining a stable vehicle posture by controlling the damping force of a suspension so as to suppress the rolling of the vehicle.
If results of detection by various sensors, such as an acceleration sensor, a yaw rate sensor, etc., are read to control various apparatus installed in a vehicle, it is a common practice to determine whether each sensor functions normally. For example, if the level of a detection signal from a sensor is out of a predetermined range, it is determined that the sensor has a failure. Then, an appropriate action is taken; for example, a predetermined control process is prohibited.
However, the level of a detection signal from a sensor can go out of a predetermined range due to an effect of impact caused by a collision. In such a case, it is determined that the sensor has a failure, even though the sensor actually functions in a normal manner. Thus, if a predetermined control is performed after occurrence of a collision, the control may fail to fully achieve its advantages in some cases.
It is an object of the invention to provide vehicle control apparatus and vehicle control methods capable of preventing a false determination that a sensor has a failure at the time of a collision, and therefore capable of performing a good control even after the collision as long as the sensor functions normally.
A first aspect of the invention relates to a vehicle control apparatus for controlling a running state of a vehicle, including at least one detector that detects the running state of the vehicle, and a controller that receives a result of detection by the detector and controls a predetermined vehicle-installed apparatus. The controller also determines whether the detector has failed, restricts a control process by which the controller controls the vehicle running state if it is determined that the detector has failed, detects a collision state of the vehicle, and, if the collision state of the vehicle is detected, changes a determining process of determining whether the detector has failed so as to restrict determination that the detector has failed, for a predetermined time following detection of the collision state.
The xe2x80x9cpredetermined timexe2x80x9d means a period of time during which at least a collision state is detected.
The controller determines whether a failure has occurred in the detector. If a failure of the detector is detected, the controller restricts the control process performed by the controller; for example, the controller prohibits a running state control operation from being started by the controller.
If in this case, the collision state of the vehicle is detected, the controller changes the determining process by which the detector is determined to have failed in such a direction as to restrict the determination that the detector has failed; for example, the controller changes the threshold for failure determination, or prohibits determination that the detector has failed. Therefore, even if an excessively great detection result is temporarily output from the detector due to the effect of an impact caused by a collision or the like, it is possible to avoid an event that it is immediately determined that the detector has failed.
The period during which the failure determination is changed is within a period during which at least the collision state is detected. The normal failure determination process preferably is restarted immediately after the collision state ends.
In accordance with a second aspect of the invention, a vehicle control apparatus for controlling a running state of a vehicle includes at least one detector that detects the running state of the vehicle, and a controller that receives a result of detection by the detector and controls a predetermined vehicle-installed apparatus. The controller also determines whether the detector has failed, restricts a control process by which the controller controls the vehicle running state if it is determined that the detector has failed, detects a collision state of the vehicle, and, if the collision state of the vehicle is detected, prohibits the restricting operation of the control process of the controller for a predetermined time following detection of the collision state.
The xe2x80x9cpredetermined timexe2x80x9d means a period of time during which at least a collision state is detected.
The controller determines whether a failure has occurred in the detector. If a failure of the detector is detected, the controller restricts the control process performed by the controller; for example, the controller prohibits a running state control operation from being started by the controller.
If in this case, the collision state of the vehicle is detected, the restricting operation of the controller is prohibited; for example, the running state control operation is continued as normal, regardless of the determination as to whether the detector has failed. Therefore, even if an excessively great detection output is temporarily produced from the detector due to the effect of an impact caused by a collision or the like so that it could be determined that a failure has occurred in the detector, it is possible to avoid an event that the restriction of the control process is performed during the collision.
The period during which the restricting operation is prohibited is within a period during which at least the collision state is detected. After this predetermined period elapses, the normal restricting process is allowed immediately following the end of the collision state. Therefore, if the detector actually has a failure, the control process of the controller is restricted at the elapse of the predetermined period.
In accordance with a third aspect of the invention, a vehicle control apparatus for controlling a running state of a vehicle includes at least one detector that detects the running state of the vehicle, and a controller that receives a result of detection by the detector and controls a predetermined vehicle-installed apparatus. The controller also determines whether the detector has failed, restricts a control process by which the controller controls the running state of the vehicle if it is determined that the detector has failed, detects a collision state of the vehicle, and, if the collision state of the vehicle is detected during a control of the vehicle running state by the controller, prohibits the restricting of the control process and restrains a change in a control state under the control process for a predetermined time following detection of the collision state, and, after an elapse of the predetermined time, cancels prohibition of the control process and restarts the control process by the controller.
The xe2x80x9cpredetermined timexe2x80x9d means a period of time during which at least a collision state is detected.
In some cases, a collision state of the vehicle is detected during the vehicle running state control operation performed by the controller. If in such a case, the vehicle running state control process is stopped as for example, the control state under the control may immediately change and may therefore dismay a driver. Furthermore, due to the effect of an impact caused by a collision, an excessively great detection result may be temporarily output from the detector. If a normal control is continued in such a case, the effect of the excessively great detection result may change the control state so that the driver may be dismayed.
Therefore, for the predetermined time following the detection of the collision state, the restricting of the control process is prohibited so that change in the control state is restrained. Thus, while the collision state is being detected, change in the control state is restrained. Therefore, it becomes possible to avoid an event that the drive is dismayed due to a change in the control state. After the predetermined time elapses, the prohibition of the restricting is canceled. Therefore, at this time point, the control process will be restricted if the detector actually has failed. If the detector functions normally after the collision, the control by the controller is restarted. Therefore, the effect of the control can be fully obtained until the vehicle comes to a stop.
In the first to third aspects of the invention, the controller may control a braking force applied to each wheel so as to stabilize a vehicle behavior of the vehicle.
If the controller controls the vehicle behavior, the vehicle control apparatus in accordance with the first or second aspect is able to perform a predetermined behavior control even during a collision state because the vehicle control apparatus avoids transition to a control designed to be executed at the time of failure of the detector at least during the collision state. In the vehicle control apparatus of the third aspect, the change in the control state under the behavior control is restrained while the collision state is being detected. After the collision state ends, a good vehicle behavior control can be performed until the vehicle comes to a stop, provided that the detector functions normally.
Therefore, during a period from occurrence of a collision state to the stop of the vehicle, the effect of the vehicle behavior control for stabilizing the behavior of the vehicle can be fully obtained without causing a driver discomfort due to a change in the control state.